There is a construction machine provided with a lower traveling body and an upper revolving body rotatably that is attached to this lower traveling body via a revolving mechanism. In this case, an operator gets into an operator's cab provided in the upper revolving body to operate an operating lever that is traveling operation means thereby to move the construction machine forward or backward. In cases of such traveling, although the front and the sides of the machine can be checked (visually checked) by naked eyes of the operator through a window part provided in the operator's cab, in order to look the rear of the operator's cab, there is a need for the operator to do visual check by turning his head and body. Thus, there is a construction machine provided with a surveillance camera on a rear surface of a counter weight or the like of the upper revolving body as well as a monitoring device for displaying images from this camera in the operator's cab (for example, refer to Japanese Patent Application Laid-Open No. 140619 (1998) and Japanese Patent Application Laid-Open No. 286971 (1999). That is, disclosed is a construction machine in which images of the direction of traveling backward are displayed on a monitoring device in the case of backward traveling.
However, in the case where a camera is disposed on a rear surface of a counter weight as described above, there are cases where the camera position is at a relatively high position and thus surveillance (visual check) for a lower part adjacent to the construction machine is not sufficient. Accordingly, it happens that the lower traveling body comes into contact with an obstacle or is stuck in a recess, whereby safe traveling is difficult. In particular, part of the construction machine is not displayed in an image displayed on the monitoring device, and even if there is an obstacle and the obstacle is displayed, it is difficult to grasp the distance between the obstacle and the construction machine, whereby it is difficult to say that its practicability is sufficient.
Conventionally, there are cases where vehicle body conditions (that are operating conditions of various equipment and structural members loaded in the construction machine and are, for example, conditions such as the temperature of working fluid employed in an oil hydraulic circuit, the temperature of engine cooling water, and the like) are displayed. In such cases, it is often the case that both the screen displaying vehicle body conditions and the image from the surveillance camera are displayed on one monitoring device. For this, there is a need to provide a change-over switch between the screen displaying vehicle body conditions and the image of the surveillance camera and to operate this change-over switch. However, in this case, the change-over switch is arranged on a region located apart from a traveling lever which is for making the lower traveling body travel, and therefore it is difficult for the operator to operate the change-over switch. Thus, it can be thought that without performing any switching operation for the change-over switch or the like, images in the direction of traveling backward are displayed on a monitoring device automatically when a lower traveling body is in the backward traveling condition. However, when the lower traveling body travels forward, if the upper revolving body is in a turning around condition, the operator regards the construction machine as being traveling backward. In this case, even though a surveillance camera is provided, surveillance by this surveillance camera is not performed, and the camera is useless.
The present invention was made to solve the above-mentioned conventional drawbacks, and it is an object of the present invention to provide a construction machine in which surveillance for backward states can reliably be performed and work safety can be improved.